Production of a biopesticide based on Bacillus thuringiensis subsp. kurstaki, in the laboratory

Abstract

In Colombia, the widespread utilization of bioinsecticides such as Bacillus thuringiensis (Bt) has to be supported with products that can compete both in price and availability with chemical pesticides. The objective of this work was to study different nutrients derived from agro-industrial sources, for the produc­tion of B. thuringiensis subsp. kurstaki (Btk) and to optimize the process in a 1-liter fermenter. With this purpose, biomass and spores production was followed-up spectro­photometrically and by plating in Luria Bertani medium (LB), respectively. Further­more, the toxicity of the final product was evaluated on larvae ofSpodopterafrugiperda (Lep: Noctuidae) using a diet surface bioas­say. The present work allowed the design of a culture medium that yields the following re­sults in a 1-liter fermentation: Biomass 4,03 g/ 1, spore concentration 21„10⁷ sp/ml, potency 1.284.002 Ul/ml, price US$0,03/1. These re­sults are highly promising, because the me­dium is economic, produces an acceptable quantity of spores and biomass and the latter exhibits high toxicity on lepidopterous larvae.